The size and thickness of portable wireless communication apparatuses, such as mobile phones, have been rapidly reduced. In addition, the portable wireless communication apparatuses have been transformed from apparatuses to be used only as conventional telephones, to data terminals for transmitting and receiving electronic mails and for browsing web pages of WWW (World Wide Web), etc. Further, since the amount of information to be handled has increased from that of conventional audio and text information to that of pictures and videos, a further improvement in communication quality is required. In such circumstances, there are proposed a multiband antenna apparatus and a small antenna apparatus, each supporting a plurality of wireless communication schemes. Further, there is proposed an array antenna apparatus capable of reducing electromagnetic couplings among antenna apparatuses each corresponding to the above mentioned one, and thus, performing high-speed wireless communication.
According to an invention of Patent Literature 1, a two-frequency antenna is characterized by: a feeder, an inner radiation element connected to the feeder, and an outer radiation element, all of which are printed on a first surface of a dielectric substrate; an inductor formed in a gap between the inner radiation element and the outer radiation element printed on the first surface of the dielectric substrate to connect the two radiation elements; a feeder, an inner radiation element connected to the feeder, and an outer radiation element, all of which are printed on a second surface of the dielectric substrate; and an inductor formed in a gap between the inner radiation element and the outer radiation element printed on the second surface of the dielectric substrate to connect the two radiation elements. The two-frequency antenna of Patent Literature 1 is operable in multiple bands by forming a parallel resonant circuit from the inductor provided between the radiation elements and a capacitance between the radiation elements.
An invention of Patent Literature 2 is characterized by forming a looped radiation element, and bringing its open end close to a feeding portion to form a capacitance, thus a fundamental mode and its harmonic modes occur. By integrally forming a looped radiation element on a dielectric or magnetic block, it is possible to operate in multiple bands, while having a small size.